AN OPTIMAL MULTILAYERED QUASI AMORPHOUS CVD-TITANIUM BARRIER TO FURTHER IMPROVE THERMAL STABILITY IN COPPER METALLIZATION

摘要

TiCl{sub}4 and H{sub}2 reactants are used to deposit ultrathin (10 nm) Ti films by low-temperature (<500°C) plasma enhanced chemical vapor deposition (PECVD). The as-deposited Ti film has an amorphous structure from GIXRD and XTEM analyses. Ammonia plasma is further employed to post -treat the amorphous-Ti barrier layer. Amorphous TiN{sub}x layer forms on the surface of the amorphous-Ti layer after in-situ ammonia plasma post-treatment. The resulted film has a multilayered amorphous Ti/TiN{sub}x structure, and the effective resistivity of resulted Ti/TiN{sub}x film reduces to 122 mW-cm. The barrier performance of amorphous Ti, and Ti/TiN{sub}x films are investigated by measuring leakage current densities of Cu/barrier/n{sup}+-p junction diodes after thermal stressing. Improved barrier capability against Cu diffusion is found for the Ti/TiN{sub}x barrier layer since the Cu/TiN{sub}x/Ti/n{sup}+-p junction diodes retain low leakage current densities even after annealing at 500°Cfor 1 hour. Ti/TiN{sub}x barrier layers present lengthened grain structures to effectively impede Cu diffusion, and thus act as much more effective barriers than conventional Ti films.